• 한국세라믹학회지
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• 제32권8호
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• pp.915-921
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• 1995

The morphotropic phase boundary and phase transitions of the solid solutiion system, (1-x)(Na1/2Bi1/2)TiO3-PbTiO3＋xPbTiO3 were studied by investigating changes in crystal structure, variations in permittivity with temperature, and calorimetric behavior. It was observed that the morphotropic phase boundary (MPB) of this solid solutiion system was at near 14 mol% of PbTiO3. Compositions containing less than 10mol% PbTiO3 (x<0.1) exhibited a phase transition, i.e. ferroelectric rhombohedrallongrightarrowparaelectric paraelectric cubic, with increasing temperature. Composition containing more than 14 mol% PbTiO3 (x 0.14) showed a phase transition from ferroelectric tetragonal to paraelectric cubic. In the composition range of 0.1$\varepsilon$ (T) curve, which coincided with a phase transition from ferroelectric rhombohedral to an intermediate phase, was also found.

• The Korean Journal of Ceramics
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• 제6권1호
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• pp.6-8
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• 2000

The specific heat of a partly deuterated triglycine selenage (DTGSe) crystal under $\gamma$-irradiation was measured. It was shown that $\gamma$-irradiation defects changed the thermodynamic behavior of DTGSe crystal in a small dose region. The order of the phase transition changed from the first to the second at D=0.3 MR.

• 한국세라믹학회지
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• 제43권7호
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• pp.389-392
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• 2006

Electric field-induced phase transition from the tetragonal to rhombohedral phase was investigated for the <111> direction in tetragonal PZN-PT single crystals, which have spontaneous polarization along the <001> direction. From the strain and dielectric data, it was confirmed that the samples followed a tetragonal-orthorhombic-rhombohedral phase transition sequence with application of an electric field. This transition is different from the rhombohedral-tetragonal phase transition of <001> rhombohedral composition single crystals, in which a phase transition occurred without showing the intermediate orthorhombic phase.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2012년도 제42회 동계 정기 학술대회 초록집
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• pp.573-573
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• 2012

High quality $VO_2$ thin films were successfully grown on GaN substrate by optimizing oxygen partial pressure during the growth using RF sputtering technique. The $VO_2$ thin film grown on GaN substrate exhibited an unusual metal insulator transition behavior, which was known to be observed only either in doped sample or under uniaxial stress. Raman spectra also confirmed that metal insulator transition occurred from monoclinic M1 to rutile R phase via monoclinic M2 phase with increasing temperature. We believe that large lattice mismatch between $VO_2$ and GaN substrate may cause M2 phase to be thermodynamically stable. Optical transmittance and its electrical switching behavior were carefully investigated to elucidate the underlying physics of its metal insulator transition behavior. This study may lead to a unique opportunity to better understand the growth mechanism of M2 phase dominant $VO_2$ thin films.

• 한국재료학회:학술대회논문집
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• 한국재료학회 2007년도 추계학술발표대회 및
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• pp.74.1-74.1
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• 2007

• Macromolecular Research
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• 제17권5호
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• pp.313-318
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• 2009

The side chain liquid crystal triblock copolymers (TBCs), which underwent phase transitions below their decomposition temperature, were prepared by copolymerization of poly(n-butyl acrylate) and a comonomer containing the mesogenic azobenzene group. The physical properties of TBCs in the distinctive transition temperature ranges were investigated in terms of the liquid crystal (LC) content in the copolymers. The phase transition temperatures traced optically, thermally and rheologically were well coincided one another and clearly exhibited the phase transition of smectic-nematic-isotropic with increasing temperature. In the smectic phase, increasing temperature made the liquid crystal system more elastic, but viscosity (${\eta}'$) remained almost constant. In the nematic phase, increasing temperature abruptly decreased ${\eta}'$ and G', ultimately leading to isotropic phase. Both smectic and nematic phases exhibited Bingham viscosity behavior but the former gave much greater yield stress at the same LC content.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2014년도 제46회 동계 정기학술대회 초록집
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• pp.424.1-424.1
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• 2014

Vanadium dioxide (VO2) is a strongly correlated oxide exhibiting a first-order metal-insulator transition (MIT) that is accompanied by a structural phase transition from a low temperature monoclinic phase to a high-temperature rutile phase. VO2 has attracted significant attention because of a variety of possible applications based on its ultrafast MIT. Interestingly, the transition nature of VO2 is significantly affected by stress due to doping and/or interaction with a substrate and/or surface tension as well as defects. Accordingly, there have been considerable efforts to understand the influences of such factors on the phase transition and the fundamental mechanisms behind the MIT behavior. Here, we present the influences of oxygen deficiency, hydrogen doping, and substrate-induced stress on MIT phenomena in single-crystalline VO2 nanobeams. Specifically, the work function and the electrical resistance of the VO2 nanobeams change with the compositional variation due to the oxygen-deficiency-related defects. In addition, the VO2 nanobeams during exposure to hydrogen gas exhibit the reduction of transition temperature and the complex phase inhomogenieties arising from both substrate-induced stress and the formation of the hydrogen doping-induced metallic rutile phase.

• 한국결정성장학회지
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• 제30권3호
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• pp.110-116
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• 2020

MLCC(Multi-Layer Ceramic Capacitor)의 유전체 층에 사용되는 BaTiO₃ 입자는 안정한 TCC(Temperature Characteristics of Capacitance) 거동을 갖기 위해 core/shell 구조를 갖는다. 지금까지 shell의 특성은 core/shell 구조의 전체 특성에서 유추해 왔다. 이는 core/shell 구조가 겨우 수 ㎛의 작은 크기로 shell 특성만 구별해서 측정하기가 어렵기 때문이다. 본 실험에서는 micro-contact법을 이용하여 확산쌍 시편의 계면에 형성된 확대된 core/shell 구조에 Pt 전극을 증착하여 35~135℃ 에서 shell 영역의 독립적인 TCC 거동을 측정하였다. 그 결과, 65℃에서 최대 유전율 값을 갖는 완만한 피크의 확산 상전이(Diffusion Phase Transition) 거동인 core의 특성과 구별되는 거동을 관찰하였으며, 이는 core/shell 구조의 온도-유전거동을 묘사하는 모델링에서 실험 자료로 활용될 것으로 본다.

• 한국자기학회:학술대회 개요집
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• 한국자기학회 2011년도 자성 및 자성재료 국제학술대회
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• pp.155-155
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• 2011

• Macromolecular Research
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• 제15권7호
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• pp.656-661
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• 2007

The effects of a neutral solvent of dioctyl phthalate (DOP) on the phase behavior of symmetric polystyrene-block-poly(n-butyl methacrylate) copolymers (PS-b-PnBMA) were assessed herein. Closed-loop phase behavior with a lower disorder-to-order transition (LDOT) and an upper order-to-disorder transition (UODT) was observed for PS-b-PnBMA/DOP solution when the quantity of DOP was carefully controlled. When the molecular weight of PS-b-PnBMA became larger, the LDOT did not appreciably change at smaller quantities of DOP. With larger quantities of DOP, the reduction in the UODT is greater than the increase in the LDOT. This behavior is discussed in accordance with a molecular theory predicated on a compressible random-phase approximation.